The Great Earthquake at New Madrid, a 19th-century woodcut from Devens' Our First Century (1877)
The
1811–1812 New Madrid earthquakes were an intense
intraplate earthquake
series beginning with an initial earthquake of moment magnitude
(7,5 -7,9) on December 16, 1811 followed by a moment magnitude 7,4
aftershock on the same day. They remain the most powerful earthquakes to
hit the contiguous United States east of the Rocky Mountains in
recorded history. They, as well as the seismic zone of their occurrence, were named for the
Mississippi River town of
New Madrid, then part of the
Louisiana Territory, now within
Missouri.
There are estimates that the earthquakes were felt strongly over
roughly 130,000 square kilometers, and moderately across nearly 3
million square kilometers. The
1906 San Francisco earthquake, by comparison, was felt moderately over roughly 16,000 km
2.
New Madrid fault and earthquake-prone region considered at high risk today
The three earthquakes and their major aftershocks
- December 16, 1811, 08.15 UTC (2:15 a.m.); (M 7,5 -7,9)
epicenter in northeast Arkansas. It caused only slight damage to
manmade structures, mainly because of the sparse population in the
epicentral area. The future location of Memphis, Tennessee, experienced level IX shaking on the Mercalli intensity scale. A seismic seiche
propagated upriver, and Little Prairie (a village that was on the site
of the former Fort San Fernando, near the site of present-day Caruthersville, Missouri) was heavily damaged by soil liquefaction.
- December 16, 1811 (aftershock), 14.15 UTC (8:15 a.m.); (M 7,4) epicenter in northeast Arkansas. This shock followed the first earthquake by five hours and was similar in intensity.
- January 23, 1812, 15.00 UTC (9:00 a.m.); (M 7,3 -7,6) epicenter in the Missouri Bootheel. The meizoseismal area
was characterized by general ground warping, ejections, fissuring,
severe landslides, and caving of stream banks. Johnson and Schweig
attributed this earthquake to a rupture on the New Madrid North Fault.
This may have placed strain on the Reelfoot Fault.
- February 7, 1812, 09.45 UTC (3:45 a.m.); (M 7,5 -8,0) epicenter near New Madrid, Missouri. New Madrid was destroyed. In St. Louis, Missouri,
many houses were severely damaged, and their chimneys were toppled.
This shock was definitively attributed to the Reelfoot Fault by Johnston
and Schweig. Uplift along a segment of this reverse fault created temporary waterfalls on the Mississippi at Kentucky Bend, created waves that propagated upstream, and caused the formation of Reelfoot Lake by obstructing streams in what is now Lake County, Tennessee.
There were many more aftershocks including one magnitude 7 aftershock
to December 16, 1811 earthquake which occurred on December 17, 1811 at
0600 UTC (12:00 a.m.) and one magnitude 7 aftershock to February 7, 1812
earthquake which occurred on the same day at 0440 UTC (10:40 p.m.).
Eyewitness accounts
John Bradbury, a Fellow of the
Linnean Society, was on the Mississippi on the night of December 15, 1811, and describes the tremors in great detail in his
Travels in the Interior of America in the Years 1809, 1810 and 1811, published in 1817.
After supper, we went to sleep as usual: about ten o'clock, and in the
night I was awakened by the most tremendous noise, accompanied by an
agitation of the boat so violent, that it appeared in danger of
upsetting ... I could distinctly see the river as if agitated by a
storm; and although the noise was inconceivably loud and terrific, I
could distinctly hear the crash of falling trees, and the screaming of
the wild fowl on the river, but found that the boat was still safe at
her moorings.
By the time we could get to our fire, which was on a large flag in the
stern of the boat, the shock had ceased; but immediately the
perpendicular banks, both above and below us, began to fall into the
river in such vast masses, as nearly to sink our boat by the swell they
occasioned ... At day-light we had counted twenty-seven shocks.
On the 16th of December, 1811, about two o'clock, a.m., we were visited
by a violent shock of an earthquake, accompanied by a very awful noise
resembling loud but distant thunder, but more hoarse and vibrating,
which was followed in a few minutes by the complete saturation of the
atmosphere, with sulphurious vapor, causing total darkness. The screams
of the affrighted inhabitants running to and fro, not knowing where to
go, or what to do—the cries of the fowls and beasts of every
species—the cracking of trees falling, and the roaring of the
Mississippi— the current of which was retrograde for a few minutes,
owing as is supposed, to an irruption in its bed— formed a scene truly
horrible.
John Reynolds (February 26, 1788 – May 8, 1865) who was the 4th
governor of Illinois, among other political posts, mentions the earthquake in his biography
My Own Times: Embracing Also the History of My Life (1855):
On the night of 16th November [sic], 1811, an earthquake occurred, that
produced great consternation amongst the people. The centre of the
violence was in New Madrid, Missouri, but the whole valley of the
Mississippi was violently agitated. Our family all were sleeping in a
log cabin, and my father leaped out of bed crying aloud "the Indians are
on the house" ... We laughed at the mistake of my father, but soon
found out it was worse than the Indians. Not one in the family knew at
the time that it was an earthquake. The next morning another shock made
us acquainted with it, so we decided it was an earthquake. The cattle
came running home bellowing with fear, and all animals were terribly
alarmed on the occasion. Our house cracked and quivered, so we were
fearful it would fall to the ground. In the American Bottom many chimneys were thrown down, and the church bell in Cahokia sounded by the agitation of the building. It is said the shock of an earthquake was felt in Kaskaskia in 1804, but I did not perceive it. The shocks continued for years in Illinois, and some have experienced it this year, 1855.
The
Shaker diarist Samuel Swan McClelland described the effects of the earthquake on the Shaker settlement at
West Union (Busro), Indiana, where the earthquakes contributed to the temporary abandonment of the westernmost Shaker community.
Reelfoot Rift
Geologic setting
The underlying cause of the earthquakes is not well understood, but
modern faulting seems to be related to an ancient geologic feature
buried under the Mississippi River alluvial plain, known as the
Reelfoot Rift. The New Madrid Seismic Zone (NMSZ) is made up of reactivated
faults that formed when what is now North America began to split or
rift apart during the breakup of the
supercontinent Rodinia in the
Neoproterozoic Era (about 750 million years ago). Faults were created along the rift and
igneous rocks formed from
magma that was being pushed towards the surface. The resulting rift system failed but has remained as an
aulacogen (a scar or zone of weakness) deep underground.
In recent decades minor earthquakes have continued.
The epicenters of over 4,000 earthquakes can be identified from
seismic measurements taken since 1974. It can be seen that they
originate from the seismic activity of the Reelfoot Rift. The zone
which is colored in red on the map is called the New Madrid Seismic Zone.
New forecasts estimate a 7 to 10 percent chance, in the next 50 years,
of a repeat of a major earthquake like those that occurred in
1811–1812, which likely had magnitudes of between 7,6 and 8,0. There is
a 25 to 40 percent chance, in a 50-year time span, of a magnitude 6,0
or greater earthquake.
In a report filed in November 2008, the U.S.
Federal Emergency Management Agency
warned that a serious earthquake in the New Madrid Seismic Zone could
result in "the highest economic losses due to a natural disaster in the
United States," further predicting "widespread and catastrophic"
damage across Alabama, Arkansas, Illinois, Indiana, Kentucky,
Mississippi, Missouri, and particularly Tennessee, where a 7,7
magnitude quake or greater would cause damage to tens of thousands of
structures affecting
water distribution,
transportation systems, and other vital infrastructure.
4000 earthquake reports since 1974
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